Programmable multi-channel wellplate filling stations are widely used by laboratory workers to fill wellplates with liquid reagent. A 96-well plate includes eight (8) rows and twelve (12) columns of wells each spaced apart at a nine (9) millimeter centerline to centerline distance. A 384-well plate include sixteen (16) rows and twenty four (24) columns of wells each spaced apart at a centerline to centerline distance of 4.5 millimeters. Most available multi-channel wellplate filling systems have either 8 channels or 16 channels for simultaneously filling 8 or 16 wells in a column on the wellplate. Normally, an 8-channel filling system is used to fill 96-well plates, whereas either an 8-channel or a 16-channel filling system is used to fill 384-well plates. Some 8-channel or 16-channel systems can be used to fill 1536-well plates.
There are several types of multi-channel wellplate filling stations. One type uses a peristaltic pump and tubing set to transfer fluid from a reagent bottle to wells on a wellplate. A typical 8-channel system has a linear array of filling nozzles located on a removable cartridge to which a tubing set having eight (8) flexible tubes is connected such that the tubes are in fluid communication with the filling nozzles. The tubing set is mounted through a peristaltic pump. The open ends of the flexible tubes are placed within a reagent bottle and the peristaltic pump is controlled to pump liquid reagent through the filling nozzles into one column of wells on a wellplate. The position of a wellplate platform on the filling station is indexed to the position of the next column on the wellplate under the array of filling nozzles prior to filling the next column of wells with reagent form the bottle.
The tubing set is calibrated by pre-stretching a portion of each respective flexible tube between pump mounting heads. The peristaltic pump operates on the pre-stretched portions of the flexible tubes to transfer metered amounts of liquid as directed by the controller into wells on a wellplate in the filling station. Before operating the filling station, it is necessary to prime the tubing set which entails placing the open ends of the flexible tube in the reagent bottle and running the peristaltic pump in order to fill each of the flexible tubes in the tubing set. Normally, a waste trough is provided next to the wellplate platform in order to dispense waste reagent. Waste can occur during the priming step or during other steps of the filling process. Once the pre-stretched flexible tubes are fully primed, it is also common to run the pump to dispense the first dispense into the waste trough. Discarding the first dispense is known to improve the accuracy of such filling systems. Then, the controller then operates the drive mechanisms and the peristaltic pump to transfer metered amounts of liquid reagent into the column of wells positioned underneath the array of filling nozzles and reposition the wellplate under the array of filling nozzles. After the filling operation is complete, it is common for the system to dispense the reagent remaining in the flexible tubes into the waste trough.
One of the drawbacks of such a flow-through system is that the flexible tubes of the tubing set require a relatively large residual volume in order for the system to operate. Such flow-through systems are therefore particularly ineffective when the laboratory worker has only a small amount of liquid reagent or in circumstances where the liquid reagent is a valuable commodity.